Superplastic forming module is used to analyze the formability of sheet metal under superplastic temperature and subjected to applied pressure. The setup of forming process is similar to the forming process using common sheet metal, with an exception for the Process setup described in the following section.
Figure 8.2.116 Superplastic forming
Process page enables the setup of basic process parameter for superplastic forming such as pressure curve, percent to terminate, tool contact, desired strain rate, termination time, etc. The user can modify process parameters according to practical situation. Process page for superplastic forming is illustrated in Figure 8.2.117.
The user can select one or two phase analysis. If one phase analysis is selected, the sheet is directly formed into the final part shape by applied pressure. If two phase analysis are selected, preforming is performed in the first phase to partially or fully make the sheet to confront to preformed die. In second phase, reverse pressure is applied to confront the sheet to die geometry to obtain the final part shape. Pressure and reverse pressure are usually used for superplastic forming process to obtain even part thickness.
PHASE I
Define parameters such as pressure curve, percent to terminate and contact tool.
PRESSURE CURVE
Click on <none> button to define pressure curve using EDIT LOAD CURVE dialog box described in previous section.
CONTACT TOOL
Select tools contacting with sheet.
PERCENT TO TERMINATE
Enter the contact node percent between sheet and selected contact tool. The user can use contact node percent to control the termination time of this phase. If the sheet contacts with 80% nodes of the contact tool, this forming phase is terminated.
Figure 8.2.117 Process page
PERCENT TO AUTOJUMP
Key in the contact node percent in this field if autojump option is selected in the Advanced dialog box. The current phase is automatically terminated if the contact nodes reach the input percent.
PHASE II
If part is formed in two phases, the definition of parameters for Phase II is added to the interface. The definition of parameter for Phase II is similar to Phase I. Refer to the above description.
COMMON
DESIRED STRAIN RATE (ERATE)
Set desired strain rate. Strain rate is the derivative of equivalent plastic strain with respect to time.
ADVANCED
Set advanced forming parameters. Refer to LS-DYNA User’s Manual for description about advanced setting.
Figure 8.2.118 Advance setting for superplastic forming